


Something Most Unbreakable

by YukiNoodle



Category: Ao no Exorcist | Blue Exorcist
Genre: Angel/Demon Relationship, Blood and Violence, Despair, F/M, Fear, Hope, Implied/Referenced Underage, Love, Major Original Character(s), Minor Character Death, Minor Original Character(s), Original Character Death(s), Pain, Romance, Sacrifice, War
Language: English
Status: In-Progress
Published: 2020-08-03
Updated: 2020-08-08
Packaged: 2021-03-06 06:41:22
Rating: Mature
Warnings: Creator Chose Not To Use Archive Warnings, Graphic Depictions Of Violence, Major Character Death, Underage
Chapters: 2
Words: 3,119
Publisher: archiveofourown.org
Story URL: https://archiveofourown.org/works/25679020
Author URL: https://archiveofourown.org/users/YukiNoodle/pseuds/YukiNoodle
Summary: Something dark will befall the world. Something that will intertwine the paths of two destined. One, a holy child of light; the other, a spawn with blood from the depths of hell. A demonic king of pain and fear, known as Malice, craves ultimate power and invincibility in both Gehenna and Assiah. The world's fate is put in the hands of Yukio Okumura and Musume Sakura. But perhaps a bond most unbreakable isn't enough to save the world?Note: This is a Yukio Okumura love story. All material canon to Blue Exorcist is not of my making. Mature for violence and suggestive themes
Relationships: Okumura Yukio & Original Female Character(s)
Kudos: 8





	1. Beginnings

**Author's Note:**

> I do not own any of the mentioned canonical characters, settings, things, etc. from the Blue Exorcist. Those would belong to the creator. I own only my own characters, places, things, etc. Please support the official material. Thank you for reading!!

Deep, sapphire eyes that belonged to none other than Musume Sakura peered down at the desk ahead, her fingers trailing over the patterns in the finely glossed wood in a delicate fashion. Yukio’s voice rang out to the rest of the class in its usual strong and firm tone. The student’s gaze traveled to her teacher, who despite his position as a teacher and exorcist, was the same age as her. When not in his lectures, he was a normal high school student: as they attended some of the same classes outside of this cram school classroom. Yukio held a piece of chalk steady in one hand and held a book with a worn spine in the other as he continued into his lecture about the current demon pharmacology subject. Nothing else was heard besides the scribbles of the other students taking notes and of course the quiet snore coming from Rin Okumura, Yukio’s older twin brother, which were bound to increase in volume at any moment. A hush had befallen Yukio’s voice as his lecture was interrupted by one loud snore leaving Rin’s sleeping form, causing the attention of the other students present to turn onto him. The young exorcist let out a low, uncommon growl before the clicking of his heels traveled across the floor as he approached his obnoxious sibling. With a loud slam of the book in his hand onto the desk in front of Rin, the demon jolted awake with a small yelp.  
  
“Gyaa! What the hell!?” Rin looked around frantically before noticing his younger brother towered in front of him, peering down with a purely unamused and annoyed expression.  
  
“If you wished to sleep, you should have stayed at home, Mr. Okumura.” His pale hand gripped the frame of his glasses to push them further up on the bridge of his nose.  
  
“Yeah… Sorry teach…” To avoid causing anymore trouble for his brother and essentially for himself, Rin quickly went back to his book and flipped through the pages until he reached the needed page. With one additional sigh, Yukio continued on with his business and traveled back to the front of the classroom and resumed his lecture. The scene made Musume crack a little smile. Her mind then went into the past as she remembered when her and Yukio first met.

Yukio was an exwire and Musume was a newly appointed exorcist candidate from a town further away from True Cross Academy. Her adopted parents, both of which were descendants of a long line of an ancient group of exorcists called Holy Knights, were assigned to a mission with Shiro Fujimoto, Yukio’s adopted father. The two were ordered to come along under the supervision of their guardians, but the two of them were separated from their superiors by the work of demons. The two exwires tried to remain calm and with sheer will and resolve, worked together to fight off the dark supernatural creatures before the three guardians reunited with them. Yukio and Musume thanked one another and complimented each other for their resilience and parted. Afterward, they would occasionally be assigned to the same missions as before and they soon became familiar with one another, soon becoming friends. Things seemed to be looking up for both of them at the time.  
  
However, due to complications and unspoken issues of Musume’s adopted parents, her path of becoming an exorcist had come to an abrupt halt. The reason for her being dropped from training and studies remained unknown to others, but in her favor, she soon became a distant memory to her colleagues. All except Yukio, who had asked his father of her condition on occasion out of general concern for her health. The whereabouts of herself and her guardians were unknown until now.  
  
“Sakura?” Yukios voice popped the student back into reality and her eyes fluttered to him in anxiety and a slight start.  
  
“Y-yes, Mr. Okumura?” she stuttered with nervousness.  
  
“Are you feeling alright?” The exorcist raised his dark brow, the confusion in his face and slightly widening eye lids brought out more of the vibrance of his teal irises. Musume quickly nodded in response.  
  
“U-um yes. I apologize for the disruption.” She gave a bow of apology. Yukio however said nothing more as he gave a small nod and continued his lecture.  
  
A few more seemingly endless minutes passed before the chime of the school’s bells rung loudly and melodically throughout the room, queueing the end of the class period and the start of lunchtime. Yukio glanced at the ceiling before heading to his podium to gather his materials for bringing them to his office as the students grabbed their belongings as well. Once he finished stacking papers, he called out to his students.  
  
“Don’t forget to start research on the medicines we went over in class and complete the assignment I handed out to each of you. Ms. Sakura, I’d like to speak with you if you do not mind donating a few minutes of your time.” Caught in mild shock by his request, Musume paused in gathering her things.  
  
“… I don’t mind.” she insisted.  
  
The light brown haired exwire stayed put, resting herself against the front of the desk while the others flooded out of the door, Rin being the most excited for lunch. Once Yukio and Musume were alone, there was a short silence before Yukio turned to face her. His face withheld a gentle expression and his eyes were soft when he approached her. Musume looked down a little, her sapphire eyes locked on the pin he wore.  
  
“Even though I’ve heard a long while ago that you became an exorcist, it still amazes me… now that I’m here, it feels like only yesterday that we were still training together as exwires...” She gave a small smile of recollection which Yukio himself returned.  
  
“Time does fly,…” he pushed his glasses up once again, “ Anyway, Musume. I wanted to know how you’re doing. I’m… not just asking as your teacher. How are you adjusting to… all of this?” The more he spoke, his voice got even lower, showing small signs of pity and empathy. The girl’s eyes almost instantly glossed over with solemnity and grief.  
  
“It’s… still hard to think about… The move into the dorms went alright but… I can’t get that image out of my head. I just can’t…” Musume didn’t have any words on her mind and Yukio didn’t seem to either for a moment as he was silent. Once he processed her words, he spoke again.  
  
“They were good people… Forgive me if I pried too much, Musume. But as your teacher and your friend… you can speak to me whenever you need to. The same goes for your studies. Please let me know if I can help...” his voice rang with comfort and the tone was soothing, cradling the girl into a slighter state of calm and content. A sigh left her light pink lips and she faced him completely.  
  
“Thank you, Yukio. Right now, I need to be strong about this… about my parents. Whatever demon it was, Mephisto is ensuring my safety as well as everyone elses.”  
  
“He assured you of that upon your arrival?”  
  
“Just before actually. Right when I was moving my things here.”  
  
“That’s good…” Another small awkward silence ensued before Yukio glanced down at the plain watch hugging his wrist. “Well, I don’t wish to keep you from your meal any longer. If you would be alright, I could accompany you.” He gave a sweet smile at the end of his offer, making his friend’s grief ease into a more positive emotion.  
  
“I wouldn’t mind. Thank you for the offer.” Her lips pursed into a smile back at him.  
  
“Of course.” He gave a small nod.

Once the exchange was over, the two gathered their things and headed out, nothing heard but the quiet shuffle of their feet and the door being closed behind them.  
  



	2. Scourge

A cool breeze gently blew through the crack of the open window on Yukio’s side of the dorm room, relieving the boys of a hot summer day as they slept in their beds. The night was quiet, only crickets chirping in the distance outside and Rin’s steady snoring from across the room. Only a few hours left until they had to get ready for the day. Rin laid sprawled out in his bed, limbs bending in a silly fashion as drool trailed from his mouth and soaked his pillow. Kuro’s sleeping form was pasted against Rin’s thigh, also resting awkwardly. Yukio rested soundly in his bed, hair laying along the fabric of the pillow and his face showing a peaceful and dreaming state of sleep. His lips were parted to where if one listened closely, his light breathing would be barely audible.  
  
He was somewhere else, standing on guard in a plain, grass field with a crimson sky and the distant shouts of battle cries flooded the area around him. The ambiance itself was enough to send a chill down the spine of any soul to witness such a thing. The worried young exorcist looked around in a frantic manner, eyes darting around with utmost anxiety. His heart raced and his mind spiraled. _Where am I? What… What’s going on?_ As he questioned his environment, the world around him became black, making him flinch and clench his teeth with unease. Blue flame clouded the vision in his eyes and a guttural snicker teased his ear drums.  
  
“I am the scourge that will bring humanity to its knees!” The voice was accompanied with blood red eyes and soon after, loud beeps rang in Yukio’s ear.  
  
_RNNNG!! RNNNG!! RNNNG!!_  
  
“-kio, wake the hell up!”  
  
“Wh-wha!?”  
  
Yukio’s teal eyes opened as he shot up from bed, panting for air and looked around in a panic before he laid eyes on his annoyed twin brother. He seemed slightly confused as he was always up before Rin until he put two and two together as his alarm was still blaring. He shut it off with shaking fingers and looked at his brother with nervousness. His eyes travelled down as Kuro stood beside Rin with innocent eyes. Kuro must have woken Rin to get Yukio out of bed. After all, it was unlike the young prodigy to sleep through his alarm like he was a moment ago.  
  
“Geez. What’s up with you? I told you, you’re overworking yourself! So tired that you can’t even get up with your clock.” The demon crossed his arms with a glare. But at this point, Yukio was still shaken up from whatever he just experienced in his sleep. People normally forget their dreams… but he couldn’t get a single moment of it out of his head.  
  
Ignoring Rin’s “big brother” attitude, Yukio gave a quick apology before getting out of bed and getting dressed in uniform for the day, leaving his twin watching with concern this time.  
  
“Yukio, are you sure you’re okay?...” his voice no longer expressed any anger as Yukio didn’t face him at all.  
  
“I’m fine Rin… The alarm just startled me a bit that’s all…” he quickly lied to just get everything out of the way and to hopefully clear his head of what happened. Rin tilted his head and gave a little sigh.  
  
“Okay then...”  
  
The raven-haired teen itched his scalp before he casually grabbed his uniform like the interaction never even happened. Yukio shook his head and pinched the bridge of his nose before finally composing himself. _It is just a meaningless nightmare and nothing more. I have far too much to do right now than to worry about a dream._ After a little self-convincing, the exorcist grabbed his needed materials and headed out of the room to finish doing what he had to before leaving the dorms.

. . .

  
With the loud chime of the bells, Yukio had his book in hand and began class. Everyone, even Rin surprisingly, had their notes and materials out and ready to go to continue where they left off the day before. The young teacher glanced in Musume’s direction, taking note that she wasn’t distracted like she was yesterday.

  
“I’ll begin class with an announcement from Japan branch HQ. There have been demonic disturbances in a forest area a while away from Academy Town. We are all to stay at a fort built by the Order with other exorcists, including the headmaster and Ms. Kirigakure, to investigate. And if it is possible, shut the disturbances down by exorcism. The said area has been fluctuating in activity drastically, so HQ has come to suspect that a demon king is behind the demonic activity.” The very announcement made Rin perk up in his seat, excited for the thought of some action on the field.  
  
“A demon king?” Rin’s tail wagged in pure glee in his seat before Yukio gave a nod of confirmation.  
  
“Yes. But that doesn’t give us the incentive to go looking without any of our superiors present. Is that clear, Mr. Okumura?” Yukio’s voice lowered a bit in an almost threatening and scolding tone at his brother, making sure he wasn’t going to take this as an opportunity to act foolishly. Rin rolled his eyes with a heavy sigh leaving his lips as he lazily waved his hand.  
  
“Alright, alright. Yes, sir.”  
  
Suguro had to resist facepalming at Rin’s childish behavior before Yukio had asked if anyone had any more questions. To that, Suguro raised his hand lightly, his eyes showing concern.  
  
“How long exactly will we be staying there, Mr. Okumura?” Yukio smiled and gave a small shrug.  
  


“I’m afraid I do not know at the moment. If I had a guess, a week at the least but depending on the severity of the situation, it could take even longer, so I suggest everyone packs everything they would need from their dorms. The headmaster has already saw to it that attendance wont be an issue with your normal high school classes. I will add that the fort is made of stone and is quite a few centuries old, but it has been modernized as much as possible by the Order. It has electricity and plumbing powered by a gigantic generator built underground and the rooms are quite large. As part of our duties, we will be assigned to random groups every day and patrolling the fort as well as the forest around it at different times. Senior exorcists will be leading each group for an acceptable amount of reinforcement if higher level demons are to show themselves. Regardless of that, it’s my responsibility to warn you all to remain vigilant. Understood?”  
  
The students all gave a nod as they listened with intrigue, unable to resist the astonishment at the idea of staying at such a place for at least a week. It would be a nice change of scenery and would be less crowded than the dorms that they sometimes feel so suffocated in. When Yukio clarified to himself that there were no further questions, he resumed class into the lesson.  
  


. . .  
  


The old boys dormitory where the twins resided alone was silent as the two were packing what they needed for the mission. Rin sloppily had his clothes sprawled out on his bed while Yukio neatly organized his clothing in his big luggage bag. The older twin looked at his brother with a sigh once he stuffed everything he needed in a few bags.  
  


“When are we going?” He put his hands on his hips as he waited for Yukio to respond. The exorcist hadn’t turned to face him but spoke otherwise.  
  
“I told you, as soon as we are finished packing.” Yukio’s voice no doubt expressed utmost annoyance as he had to repeat himself. Rin gave a giant yawn, tail limply brushing the ground as he looked out the window on his side.  
  
“This is going to be such a rad mission.” At the thought of all the fun he could have at the fort, Rin’s lips pulled back in a devilish smirk. The mischievous tone made Yukio sigh exasperatedly.  
  
“We aren’t there to fool around, Rin.”  
  
“Oh stop. We aren’t gonna dictate all of our time to work you know. You need the most relaxation anyway.”  
  
“The word is “dedicate”, Rin… but I guess you’re right. Other than patrols and combat, there would be quite a bit of time left over… even after filling out the reports I’ll be writing.” Yukio pinched the bridge of his nose as it helped him concentrate on getting his thoughts together.  
  
“See? So whatcha gonna do? You seem to be pretty talkative to that Musume girl. Are you crushing on her?” Rin smirked evilly at his teasing, but Yukio shook his head.  
  
“She happens to be a friend I’ve known for a few years now, as I have told you before. And she is going through a lot right now… I just want to help her get adjusted to everything.”  
  
“She is. We’ve talked to her for a little while since she came here, and I think she’s starting to relax a bit. Damn… you both needed this mission I guess.” Yukio was a bit shocked at Rin’s sudden seriousness, but the surprise quickly melted into relief.  
  
“So, she is doing alright?” He couldn’t hide the bittersweet joy for his friend in his voice, which made Rin hesitate a little.  
  
“Uh… yeah.” Rin scratched the back of his head after facing away from Yukio this time. _Is he sure he doesn’t have a crush?_  
  
Yukio paused for a bit as he was lost in thought about Musume doing better than she has been the past few days. It made him happy to see her opening up again like she used to. But suddenly, a different memory flickered into his mind, one that made him very uneasy. It was the dream he had the night prior. The spine-chilling voice played in his head over and over and the red eyes were stuck in his memories like a stain. _I am the scourge that will bring humanity to its knees!_ The young exorcist clenched his teeth. The nightmare forced anxious pulses from his heart and his mind spun wildly. Hardly anything worries him this much, and what was worse was that he didn’t even know why it was so bothersome. Or even why it borderline scares him. Yukio shook his head before looking back at his twin.  
  
“Are you ready to go?” There was a small trace of shaking in his voice, but Rin wasn’t fully listening.  
  
“Yeah.”  
  
“Alright… Come on then…” The two of them gathered their bags and left the dorm room to meet up with everyone at the fort.


End file.
